Hermit Crab Killer

[Nalgene00]

So I have a serial killer in my tank... This started off in October when the tank was originally set up with live rock/sand. Whatever this is has taken out all of my little blue legs and redlegs, only leaving my Polkadot hermit to survive. I moved everything into a 25 Gallon cube in February, transferring the rock, sand (rinsed), and all other inhabitants save for a handful of bristle worms I was able to pluck out. Following the transfer, I had my resident Polkadot and two Blue Eyed hermits that were moved in from a pico. One of the Blue Eyes is currently missing, and the other has a hole that has appeared in its shell.

It seems like this killer is boring a hole through the shell and then has a nice snack. Every single blue and red leg that turned up dead was found with a hole in the shell, usually a little ways back from the hole. Photos will be attached, pardon me for the reflection and quality.

I doubt it is caused by any fish, as I have a pair of perculas that host a mat of hair algae on the back wall, and a yellowtail blue damsel.

Some hitchhikers that I am aware of:
Ball Anemones
Asterina Stars
Brittle Stars
Peanut Worms
Bristle Worms (some pushing 4 inches, living in their own little burrows)

A bit off topic:
Bonus pic of the little reef following a water change this weekend. Note my monti in the top centre that decided to release the majority of its zooxanthellae about a month ago due to a stupid mistake on my part, it's on the road to recovery but it's gonna be a slow one.

 

[diverjm]

Sounds like a Whelk Snail. I got gulf live rock and sand which came with a few whelks.

 

[diverjm]

They are notorious for drilling small holes in shells although I’ve never heard of them taking out hermits before. Usually just other snails.

 

[Nalgene00]

Do you think there could be a smaller whelk hiding away in the tank? I have 4 Nassarius in the tank, however they all roam the sandbed and are accounted for at or following feedings, they all also appear to be of the same species and were purchased from the same LFS. On the teardown and transfer in February I did inspect each rock and scrub away a fair bit of hair algae. I didn't notice anything resembling a whelk or nassarius aside from those previously mentioned.

 

[ISpeakForTheSeas]

It might not be a true whelk (whelk is often used in the hobby as a catch-all term for predatory snails), but this is definitely the work of predatory snail of some kind. I've only heard of a few (typically at least somewhat larger) snail species going after hermits though, such as Agaronia propatula (an olive snail) and Triplofusus gigantea (the horse conch).

 

[Bucs20fan]

Absolutely some form of predatory snail, the boring hole is what gives it away. Youve got a killer on the lam. Time to track this fool down.

So you know what it wants to eat, time to buy some burner ceriths or astreas, and put them in a bottle trap at night and wait to catch him in the act.

 

[Nalgene00]

So the plan now is to form a little trap out of some acrylic I have lying around and throw a blue leg in it, and see what happens over the next few days.
I did notice a small burrow of sorts in the back corner of the tank near where I dropped in all the crab shells that I pulled out during the transfer. I used a little flashlight to peek in, and I saw what looked like an exoskeleton with a red(orangish)/white blotched pattern in bands. It seemed a bit on the smaller side, but I was only able to see a portion of it. I doubt I'll be able to get a photo in there but I'll give it a shot tonight.

 

[Wynter]

true crime fan here waiting for the epic conclusion of this law and order: aquatic unit episode

 

[Nalgene00]

Nothing has turned up yet, and no hermits or snails have gone missing.. Is there a possibility that my Nassarius were just being opportunistic and taking out the hermits when they had the chance?

 

[Rick's Reviews]

Following as I've never heard of a hermit killer before

 

[I never finish anythi]

Nothing has turned up yet, and no hermits or snails have gone missing.. Is there a possibility that my Nassarius were just being opportunistic and taking out the hermits when they had the chance?

Doubt it .